Renderpark

Software: Renderpark
CPU cycles from a 64 node Dec Alpha farm
Astrophysics and Supercomputing,
Swinburne University of Technology
June 2000

Palace

Model by Jorge Angles

Restoration of an old palace in Spain where paintings of
spanish painter Diego Velazquez (1599-1660)
used to hang back in the XVII century.

Rendered using distributed animation
software by Paul Bourke
June 1992

Diego Rodreguez de Silva y Velazquez was a Spanish painter who is
considered to have been the country's greatest baroque artist. He,
with Francisco de Goya and El Greco, forms the great triumvirate of
Spanish painting.
Velazquez was born in Seville on June 6, 1599, the oldest of six
children; both his parents were from the minor nobility. Between
1611 and 1617 the young Velazquez worked as an apprentice to Francisco
Pacheco, a Sevillian Mannerist painter who was also the author of
an important treatise, El arte de la pintura (The Art of Painting,
1649), and who became Velazquez's father-in-law. During his student
years Velazquez absorbed the most popular contemporaneous styles
of painting, derived, in part, from both Flemish and Italian realism.

Youthful Works

Many of his earliest paintings show a strong naturalist bias, as
does The Breakfast (circa 1618, Hermitage, Saint Petersburg), which
may have been his first work as an independent master after passing
the examination of the Guild of Saint Luke. This painting belongs
to the first of three categories, the bodeg, or kitchen piece,
along with portraits and religious scenes into which his youthful
works, executed between about 1617 and 1623, may be placed. In his
kitchen pieces, a few figures are combined with studied still-life
objects, as in Water Seller of Seville (circa 1619-20, Wellington
Museum, London). The masterly effects of light and shadow, as well
as the direct observation of nature, make inevitable a comparison
with the work of the Italian painter Caravaggio. Velazquez's religious
paintings, images of simple piety, portray models drawn from the
streets of Seville, as Pacheco states in his biography of Velazquez.
In Adoration of the Magi (1619, Museo del Prado, Madrid), for example,
the artist painted his own family in the guise of biblical figures,
including a self-portrait as well.

Velazquez was also well acquainted with members of the intellectual
circles of Seville. Pacheco was the director of an informal humanist
academy; at its meetings the young artist was introduced to such
people as the great poet Luis de Gangora y Argote, whose portrait
he executed in 1622 (Museum of Fine Arts, Boston). Such contact
was important for Velazquez's later work on mythological and classical
subjects.

Appointment as Court Painter

In 1622 Velazquez made his first trip to Madrid, ostensibly to see
(as Pacheco tells it) the royal painting collections, but more
likely in an unsuccessful search for a position as court painter.
In 1623, however, he returned to the capital and, after executing
a portrait (1623, Museo del Prado) of the king, was named official
painter to Philip IV. The portrait was the first among many such
sober, direct renditions of the king, the royal family, and members
of the court. Indeed, throughout the later 1620s, most of his efforts
were dedicated to portraiture. Mythological subjects would at times
occupy his attention, as in Bacchus or The Drinkers (1628-29, Museo
del Prado). This scene of revelry in an open field, picturing the
god of wine drinking with ruffian types, testifies to the artist's
continued interest in realism.

Trip to Italy

In 1628 Peter Paul Rubens came to the court at Madrid on a diplomatic
mission. Among the few painters with whom he associated was Velazquez.
Although the great Flemish master did not have a direct impact on
the style of the younger painter, their conversations almost
certainly inspired Velazquez to visit the art collections in Italy
that were so much admired by Rubens. In August 1629 Velazquez
departed from Barcelona for Genoa and spent most of the next two
years traveling in Italy. From Genoa he proceeded to Milan, Venice,
Florence, and Rome, returning to Spain from Naples in January 1631.
In the course of his journey he closely studied both the art of the
Renaissance and contemporaneous painting. Several of the works
executed during his travels attest to his absorption of these styles;
a notable example is Joseph and His Brothers (1630, El Escorial,
near Madrid), which combines a Michelangelesque sculptural quality
with the chiaroscuro (light-and-shadow techniques) of such Italian
masters as Guercino and Giovanni Lanfranco.

Return to Spain

On his return to Madrid, Velazquez resumed his duties as court
portraitist with the sensitive rendition Prince Balthasar Carlos
with a Dwarf (1631, Museum of Fine Arts, Boston), an image made
poignant by the young prince's death before reaching adulthood.
From the 1630s on, relatively few facts are known about the artist's
personal life, although his rise to prominence in court circles is
well documented. In 1634 Velazquez organized the decoration of the
throne room in the new royal palace of Buen Retiro; this scheme
consisted of 12 scenes of battles in which Spanish troops had been
victorious, painted by the most prestigious artists of the day,
including Velazquez himself, and royal equestrian portraits.
Velazquez's contribution to the cycle of battle pictures included
the Surrender of Breda (1634, Museo del Prado), portraying a
magnanimous Spanish general receiving the leader of defeated Flemish
troops after the siege of that northern town in 1624. The delicacy
of handling and astonishing range of emotions captured in a single
painting make this the most celebrated historical composition of the
Spanish baroque.
The second major series of paintings of the 1630s by Velazquez was
a group of hunting portraits of the royal family for the Torre de
la Parada, a hunting lodge near Madrid. Dating from the late 1630s
and early '40s are the famous depictions of court dwarfs in which,
unlike court-jester portraits by earlier artists, the sitters are
treated with respect and sympathy. Velazquez painted few religious
pictures after entering the king's employ; Saints Anthony and Paul
(late 1630s, Museo del Prado) and Immaculate Conception (circa 1644,
Museo del Prado) are notable exceptions.

Late Works

During the last 20 years of his life Velazquez's work as court official
and architect assumed prime importance. He was responsible for the
decoration of many new rooms in the royal palaces. In 1649 he again
went to Italy, this time to buy works of art for the king's collection.
During his year's stay in Rome (1649-50) he painted the magnificent
portraits Juan de Pareja (Metropolitan Museum, New York City) and Pope
Innocent X (Palazzo Doria-Pamphili, Rome). At this time he was also
admitted into Rome's Academy of Saint Luke. The elegant Venus at Her
Toilette (National Gallery, London) probably dates from this time also.
The key works of the painter's last two decades are Fable of Arachne
(1644-48, Museo del Prado), an image of sophisticated mythological
symbolism, and his masterwork, Las meninas (The Maids of Honor, 1656,
Museo del Prado), a stunning group portrait of the royal family and
Velazquez himself in the act of painting. Velazquez continued to serve
Philip IV as painter, courtier, and faithful friend until the artist's
death in Madrid on August 6, 1660. His work had a subtle impact a
century later on his greatest successor, Francisco de Goya.

Rendering on the Macintosh

Featuring StrataVision

Australasian Wheels for the Mind, April 1991

Written by Paul Bourke
Provided as an
historical document on state of the art of Macintosh rendering at the time.

Introduction

This article will discuss the techniques available for creating realistic
computer generated images of three dimensional scenes. While the discussion is
general examples will be taken from a Macintosh package called StrataVision
from Strata Inc. StrataVision provides considerable power usually associated
only with the high-end workstation products but most importantly it adds an
exceptional user interface.

Hardware requirements

It would be misleading to suggest that quality rendering is possible on the
whole range of Macintosh platforms. The resources needed such as processing
power and colour requirements mean that only the machines at middle to upper
end of the Apple product line are suitable.

Overview

The aim in rendering is to create a realistic digital image of a scene by
computer. Ultimately it is hoped to create an image where an observer cannot
tell if it is computer generated or a photograph of something real, this is the
aim of photorealism.

There are a number of stages that can be identified in the process that leads
to the final rendered image, each of these stages are described below.

Model generation

A description of the geometry of the objects in the scene is the first
requirement. This is the task of 3 dimensional modelling applications also
known as CAD packages. Since modelling and rendering are both very difficult
tasks in their own right it is unusual to encounter both within one package.
Also, while rendering can be made discipline independent, modelling is usually
very discipline dependent. The modelling requirements for desktop presentation,
engineering, and architecture are all very different. It is therefore desirable
for a rendering package to be able to read a number of 3D file formats so that
it can import the geometry data from as wide a range of modellers as possible.
StrataVision provides for the importing of DXF files as well as Super3D text
files.

The examples shown in this article will use the scene in
figure 1 which was
created using a general purpose CAD package called MicroStation.

Surface attributes specify how the surfaces that make up the objects in the
scene react to light. They include such things as the colour, reflection
coefficients, transparency, and texture. These are the most important
contributions to the quality of the rendered image since the geometry of most
objects is simple and the visual information comes from how the surfaces react
to incident light. It has been suggested that the most geometrically complex
object in a home is the telephone, the most visually appealing objects such as
a wood grain tabletop are often nothing more than rectangular boxes.

Some of the surface characteristics one would expect to be able to control are:
the red, green, blue components of the colour; the reflection coefficients for
ambient, diffuse and specular contributions; the transparency and the
refractive index; the glossiness. Each of these parameters is usually
normalized to vary between 0 and 1.

While the above can be specified numerically for an entire surface it is often
necessary to vary the parameter over the surface, this is called texture
mapping. Colour is the simplest case of an attribute that usually changes
across a surface, for example, a wood tabletop with a grain. With texture
mapping a bitmap of the colour variation is pasted onto the surface. The
texture can be scaled, positioned, and repeated with various types of tiling
systems. For textures indicating reflection coefficients only grey scale images
are used, the white areas being high reflection coefficients while the black
areas represent a low reflection coefficients. An example of a texture map for
specifying the colour variation across a surface is shown in
figure 2. This is
a grey scale scanned image subsequently coloured in with a colour painting
application.

Another common application of textures is called a bump maps which specifies
the roughness of the surface. The classic example usually cited is for
rendering oranges where the appearance of pinches in the skin can be simulated
with a bump map.

The efficient use of texture maps can greatly simplify the modelling process.
If traditional modelling and hidden line rendering were being used to model a
tile floor it would be usual to draw each tile as a separate rectangle which
can then be coloured individually. The result is a model with a large number of
objects which slows down future processing. If texture maps are possible then
the floor is modelled as one rectangular plane and the tile effect is created
with a bitmap picture representing the minimum tiling pattern.

The example scene contains a number of texture maps. Two are shown in
figure 2,
the brick also has an associated bump map. Other textures include oak plank on
the floor, the image in the picture frame, the wallpaper, the pattern on the
rug, and the cloth for the lamp shade.

This involves settings the position and attributes of the sources of light that
affect the scene. Besides the ambient or background light level, there are
generally four types of light source provided from which more complex sources
can be made. They are: suns, point sources, directional sources, and luminous
surfaces. Suns are considered to be an infinite distance away (wavefronts are
parallel). Point light sources can be placed in the scene and radiate in all
directions although they may have different distributions, circular and
cylindrical say. Directional sources provide for such things as torches or spot
lights. The angle or aperture of the cone is variable giving narrow or wide
angle beams. Luminous surfaces cover such things as fluorescent surfaces,
sometime referred to as the glow factor. All sources of course have an intensity
attribute and often only white light is provided. Making coloured sources is
accomplished by enclosing a white light source in a partially transparent
coloured sphere.

The sources can be positioned anywhere in the scene and made to point in some
direction for directional sources. Usually the source itself will not render as
anything geometrically (besides a source of light). If the structure of the
source is required then it must be created as any other part of the scene.

The example scene contains two sources and an ambient light setting. There is
one point source on the ceiling slightly behind the camera and another point
light source inside the lamp.

View settings

This is where the conceptual camera is positioned and aligned to dictate the
contents of the image. The position is simply a 3 dimensional coordinate and
the direction is specified with a pointing vector. Other camera attributes
include the focal point and the depth of field. In a windowing environment the
image "seen" by the camera is displayed within the window area.

Rendering

Finally the computer can be instructed to do its thing. There are details such
as the image resolution and size, as well as any options that apply to the
rendering algorithms. Since the time taken to compute the image as desired may
be very great there are a number short cuts that can be used to check the
status of the scene. For example the image in
figure 3 took about 2 minutes
while
figure 4 took about 6 hours on a Mac IIci.

Two of the most useful methods of previewing the image are:

Render using crude but fast rendering algorithms. This is particularly useful
for checking the position and interaction of objects in the model and the basic
colouring. These techniques are the more classical hidden line and shading
models such as Gouraud and Phong shading.

Render small areas with the rendering technique that will finally be used for
the whole image. This allows the texture mapping to verified as well as the
overall lighting levels.

The standard in user interface on the Macintosh makes it an ideal candidate for
the two most important parts of the scene description process, that of
modelling in three dimensions and the creating and assigning surface
attributes. A big advance has been made with 32 bit Quickdraw and the way the
operating system can provide tools to assist in the creation of high
quality colour graphics environment. Products such as StrataVision
and RenderMan are bringing very high
quality rendering into this environment.

This model is based upon the amphitheatre in the center of the ancient Roman city
of Jerash a few kilometers outside Amman in Jordan.
The theatre could seat around 4000 people and is similar in design
to the amphitheatre in the center of Amman.

The geometry for the model was imported into MicroStation and converted
into a PovRay scene through the WRL export, this creates the cleanest
and most convenient geometry output of all the formats provided by
AutoCAD and MicroStation.

The rendering of the model served a number of purposes. It was a suitably
complicated model to test some inhouse parallel rendering tools, it was
used to create stereo pair images and animations for a virtual reality
theatre, and it was use to experiment with precomputed interactive
environments in stereo.

Because of the AutoCAD origin of the model there was no useful colour
information available. Fortunately the entire stadium is essentially
built from the same material. An attempt was made to provide some
interesting variation in the stone colour.